The Git Tutorial - EclipseCon 2012

Chris Aniszczyk Stefan Lay Kevin Sawicki
(Twitter) (SAP) (GitHub)
The Git Tutorial
EclipseCon 2012

Matthias Sohn Benjamin Muskalla
(SAP) (Tasktop)

http://eclipse.org/jgit
http://eclipse.org/egit
http://code.google.com/p/gerrit

Agenda

Introduction

Exercises
Setup & Cloning the Sample Repository
Local Development with EGit
Gerrit Code Review
Mylyn Integration
GitHub Eclipse Support

Q&A

Copyright © C. Aniszczyk, S. Lay, B. Muskalla, K. Sawicki, M. Sohn

Git
… a distributed revision control system built by the
Linux project to facilitate code review
Distributed means no central repository
● No central authority!
● Easy offline usage
● Easy to branch a project
● Protected against manipulation by cryptographic hashes

Really good at merging
● Coordination only needed "after the fact”
● Easier to rejoin (or refresh) branches

Structured around commits (i.e. patches)
● Tools for identifying problem commits (git bisect)
● Tools for restructuring branches w/ specific commits


Git at Eclipse
JGit is a lightweight Java library implementing Git
http://www.eclipse.org/jgit/
EGit is an Eclipse Team provider for Git based on JGit
http://www.eclipse.org/egit/
Gerrit Code Review is a Git server based on JGit
adding permission control and review workflow
http://code.google.com/p/gerrit

Gerrit @ Eclipse went live
https://git.eclipse.org/r/


Eclipse is Moving to Git
CVS has been deprecated and will be retired end of 2012

Project & code repository breakdown as of 2012-03-25
http://eclipse.org/projects/scmcountdown.php

Copyright © C. Aniszczyk, S. Lay, B. Muskalla, K. Sawicki, M. Sohn, S. Zivkov

Gerrit Code Review @ Eclipse
https://git.eclipse.org/r/ is now available for all projects now used by:

EGit, Jetty, JGit,
Jubula, Libra, Lyo,
Mylyn, Platform, R4E,
Recommenders,
Skalli, Tycho

Copyright © C. Aniszczyk, S. Lay, B. Muskalla, K. Sawicki, M. Sohn, S. Zivkov

Modern Code Review – What is it ? Guido van Rossum [1]

When one developer writes code, another
developer is asked to review that code
A careful line-by-line critique
Happens in a non-threatening context
Goal is cooperation, not fault-finding
Integral part of coding process
Otherwise this will happen:
Debugging someone else's broken code
– Involuntary code review: Not so good; emotions may flare

[1] http://code.google.com/p/rietveld/downloads/detail?name=Mondrian2006.pdf


Code Review – Benefits Guido van Rossum [1]

Four eyes catch more bugs
Catch bugs early to save hours of debugging

Mentoring of new developers / contributors
Learn from mistakes without breaking stuff

Establish trust relationships
Prepare for more delegation

Good alternative to pair programming
asynchronous and across locations

Coding standards
Keep overall readability & code quality high

[1] http://code.google.com/p/rietveld/downloads/detail?name=Mondrian2006.pdf


Gerrit

git git
git git

- verify proposed
changes
- clone repository - continuous
- fetch / push changes integration builds

Developer PC
Developer PC
Hudson

git
git


Gerrit

git git
git git
master
change 12
submit accepted
change 10
change 12
change 23

fetch master fetch change 23
to get push improved
change 10 to try it
updates
Developer PC Developer PC

git git
git git


Local Development
with EGit


Gerrit

git git
git git

clone repository

Developer PC
Developer PC

git
git


Sample Application


Git Exercises

1 Setup & Clone the example repository
2 Develop a feature
3 Develop 2nd feature and use staging view
4 Work on branches in parallel
5 Fetch the latest state
6 Merging, Rebasing, Resolving Conflicts


Git Exercises

7 History view
8 Reset branch to previous state
9 Change a series of commits
10 Git blame
11 Stash
12 Submodules


Gerrit Code Review


Gerrit
Server managing central Git repositories
Gerrit


Gerrit
Access Control

Gerrit


Gerrit
Access Control

Gerrit

git push


Gerrit
Code Review

Gerrit


Gerrit
Code Review

Gerrit
git push


Gerrit
Code Review

Gerrit
git push <for_review>


Gerrit
Commenting


Gerrit
Discussing & Improving


Gerrit
Voting


Gerrit
Do not miss:

Talk by Shawn Pearce (Gerrit founder and Project Lead)

Harnessing Peer Code Reviews

Wednesday, 14:15, Ballroom A


http://git.eclipse.org/r/

Gerrit

git git
git git
- verify proposed
changes
- continuous
- clone repository integration builds
- fetch / push changes
Developer PC
Developer PC

Hudson

git
git


Gerrit Exercises

1 Configure push to Gerrit
2 Push change to Gerrit
3 Review change
4 Improve a change
5 Submit a change to the codebase
6 View Gerrit review notes
7 Starting Demo Gerrit Server (backup)


Mylyn Integration


90% Irrelevant


Task-focused IDE


< Demo >


Exercises: Mylyn Integration
1 Mylyn / EGit Integration


2 Use Gerrit from within the IDE



1 Mylyn / EGit Integration

2 Use Gerrit from within the IDE

Related talk
Wednesday, 1:30PM - 2:15PM
Build, Stage, Review, Merge: Task-focused Development the Eclipse
Mylyn Way


● https://github.com/eclipse
○ 248 mirrored repositories

● Browsing source code
● Comparing branches and tags
● Activity feeds
● Charts & graphs
● Downloading snapshots


GitHub EGit Integration
GitHub Mylyn Connector
Issues
Gists
Pull Requests
Import Wizard
GitHub Java API
Maven plugins
Reporting
Automating tasks


GitHub Exercises: EGit Integration

1 Setup Share on GitHub


Q&A


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1 Sign In: www.eclipsecon.org

2 Select Session Evaluate

3 Vote

The Git Tutorial - EclipseCon 2012

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